1. Technical Field
The present disclosure relates to a lighting apparatus capable of improving light flicker, and more particularly, to a dimming regulation circuit which is capable of reducing the occurrence of light flicker by stabilizing a rectified voltage in response to an unstable output voltage of a dimmer, and a lighting apparatus including the same.
2. Related Art
In order to reduce energy, a lighting apparatus is designed to use a light source having high light emission efficiency based on a small amount of energy. Recently, a light emitting diode (LED) has been used as a representative light source of a lighting apparatus. The LED is differentiated from other light sources in terms of various aspects such as energy consumption, lifetime, and light quality.
Since an LED is driven by a current, a lighting apparatus using an LED as a light source requires a large number of additional circuits for current driving.
In order to solve the above-described problem, an AC direct-type lighting apparatus has been developed. The AC direct-type lighting apparatus provides an AC voltage to an LED.
The AC direct-type lighting apparatus is configured to convert an AC voltage into a rectified voltage, and control an LED to emit light through current driving using the rectified voltage. Since the AC direct-type LED lighting apparatus uses a rectified voltage without using an inductor and a capacitor, the AC direct-type LED lighting apparatus has a satisfactory power factor. The rectified voltage indicates a voltage obtained by full-wave rectifying an AC voltage.
The lighting apparatus may include a power supply circuit and a control unit. The power supply circuit provides a rectified voltage using an AC voltage, and the control unit performs current control to drive the light source. In most cases, the control unit may be manufactured as one chip, and mounted in a lighting system.
In the lighting apparatus, the power supply circuit may be configured to have a dimming function. The dimming function may be performed by a dimmer employed in the power supply circuit. The dimmer is configured to determine the position at which the phase of an AC voltage is triggered in response to a change in charge voltage. That is, the dimmer outputs an AC voltage of which the phase is controlled, and the light source emits light at a brightness corresponding to the output voltage of the dimmer.
Through the above-described dimmer, the brightness of the light source of the lighting apparatus can be adjusted in the range from the level at which the light source is turned off to the level at which the light source emits light to the maximum.
In general, the dimmer has a problem in that the compatibility with a load is degraded due to a characteristic difference between internal diode alternating current switches (diac) or triode alternating current switches (triac). Due to the above-described problem, the dimmer has a limitation in providing a high-quality AC waveform.
Specifically, the dimmer may provide an output voltage to which delay is irregularly applied due to an internal RC characteristic. Furthermore, the dimmer may provide an output voltage having a waveform of which the light emission width differs due to the operation characteristic of the triac. Furthermore, the dimmer may provide a positive output voltage and a negative output voltage, which have different magnitudes (amplitude). Furthermore, when noise is introduced from the power source, the output voltage of the dimmer may be distorted.
In particular, when the phase of an output voltage is controlled at a low angle, the dimmer may provide an unstable output voltage. More specifically, when the position at which the dimmer triggers the phase is unstable, the output voltage of the dimmer may include a waveform with an unstable magnitude.
The above-described dimmer may be used in an AC direct-type lighting apparatus. In this case, a rectified voltage provided for light emission is influenced by an output voltage of the dimmer, the output voltage including a waveform of which the magnitude is unspecified. As a result, the AC direct-type lighting apparatus may irregularly emit light, thereby making a light flicker.
Therefore, the AC direct-type lighting apparatus needs to stabilize the rectified voltage which is influenced by the output voltage of the dimmer, in order to reduce light flicker.